The present invention relates to a lifting device for a roller deck used to angularly deflect transport goods such as pallets. The roller deck consists of a basic frame and a lift frame which is movable relative to the basic frame. Both frames have support rollers for transporting the pallets.
When conveying pallets in shelved storage areas, it is often necessary to deflect the pallets alone, as well as those loaded with piece goods, by 90.degree. within the tightest amount of space. For this purpose, roller decks are used which are installed at the end of the roller track. The roller deck generally consists of a basic frame, in which, for example, rollers are mounted in the same conveying direction as those of the preceding roller track. A vertically movable lift frame is associated with the basic frame, and the rollers of the lift frame retract between the rollers of the basic frame. The axes of the rollers in the lift frame are at right angle to the axes of the rollers in the basic frame. It is thereby possible to convey a pallet loaded with piece goods in one direction onto the roller deck and subsequently by raising the lift frame, to further convey the pallet in a direction at right angles to the prior direction onto an additional roller track which is mounted at a slight difference in height with respect to the first roller track.
In order to raise and lower such a roller deck, cam drives or hydraulic drives have previously been used with the aid of which a relative motion between the basic frame and the lift frame can be carried out. When cams are used, it is necessary, in case of replacement of the cam, to separate the lift frame in order to dismantle the lifting device itself. Constant maintenance of the installation is required in order to avoid premature wear. When using hydraulic lifting devices and in the case of wear of an individual lifting device, the lift frame and the basic frame must likewise be separated. In order to precisely guide the lifting device, a film anchoring of the device, namely the cylinder, is required in the basic frame as well as in the lift frame. Furthermore, steadly maintenance is indispensable and one must work with a certain excess of hydraulic fluid in order to avoid premature wear. This directly results in the dirtying of such a roller deck by hydraulic fluid.
Proceeding from this, the objective of the present invention is to carry out an exchange of worn lift elements without separation of the roller deck into basic and lift frames. At the same time, the lift elements are maintenance-free during operation. By mounting four pneumatically actuated lift bellows between the basic frame and the lift frame, and by installing four stops, raising and/or lowering of the lift frame a predetermined distance is made possible. Instead of the four pneumatically actuated bellows in the corners, between the basic frame and the lift frame, a single lift bellows can be used if it is in the central region between the basic frame and the lift frame and stops are provided at all four corners. By raising the pressure of at least one lift bellow, a significant amount of touching of the lift frame at the end settings of the stops is insured. By using air, no environmental pollution occurs within such a conveyor path since no oil is released into the atmosphere when the lift frame is lowered.
Guides for the path of travel of the lift frame are useful when using four bellows and particularly useful when using a single lift bellows. While particular stop arrangements for the path of travel of the lift frame may also be used to guide the lift frame, a separate guiding system eliminates wear of the stops.
A further development of the subject of the invention, the installation of three guides onto the roller deck is proposed. By means of these three guides, a clear precise guidance of the roller deck is assured during lifting and lowering movements.
By firmly attaching the lift bellows to the basic frame, for installations which are subject to shocks, a secure support of the lift bellows is achieved which is not required with shock-free conveying systems. It is, hereby, sufficient if the support in the basic frame is flat or slightly dish shaped. As a result of this, no additional installation labor, especially upon replacement of left bellows, is required, and a new lift bellows can be introduced between the basic frame and the lift frame in a minimal amount of time without the need for separating the two frames or providing additional support for them. According to the invention, a self-locking of the bellows between the basic frame and the lift frame is attained by maintaining a slight pressure so that the bellows do not quite raise the lift frame without providing additional anchorings on the basic frame or the lift frame. The stops serve, at the same time, as prop-like supports for supporting the lift frame on the basic frame while replacing bellows.
In order to be able to transport a sensitive material with the device according to the invention and to deflect it by 90.degree., a rubber coating of the stops is proposed. As a result of the inventive coating of the individual stops with rubber or other shock absorbing material such as rubber-like plastic, the collision of the impact of the end locations is so dampened that damage to the partially sensitive goods on the pallets does not occur. Such dampenings are not available with hydraulic drives nor with cam drives.